Semiconductor processing method using photoresist and an antireflective coating

ABSTRACT

A semiconductor processing method includes forming an antireflective coating comprising Ge and Se over a substrate to be patterned. Photoresist is formed over the antireflective coating. The photoresist is exposed to actinic radiation effective to pattern the photoresist. The antireflective coating reduces reflection of actinic radiation during the exposing than would otherwise occur under identical conditions in the absence of the antireflective coating. After the exposing, the substrate is patterned through openings in the photoresist and the antireflective coating using the photoresist and the antireflective coating as a mask. In one implementation, after patterning the substrate, the photoresist and the antireflective coating are chemically etched substantially completely from the substrate using a single etching chemistry.

TECHNICAL FIELD

[0001] This invention relates to semiconductor processing methods whichuse photoresist and antireflective coatings.

BACKGROUND OF THE INVENTION

[0002] Integrated circuitry fabrication typically involves lithographicprocessing to transfer patterns formed in an imaging layer to anunderlying substrate material which will form part of the finishedcircuitry. One example process is photolithography wherein the imaginglayer comprises a photoresist material. The photoresist material istypically formed over a layer to be patterned either by ionimplantation, etching or other processing. The photoresist is thenmasked or otherwise processed such that selected regions of thephotoresist are exposed to actinic radiation and thereby patterned. Thephotoresist is then processed in a manner which removes either theprocessed or unprocessed portions of the photoresist such that openingsextend therethrough to the underlying layer to be patterned.

[0003] One process of doing so is by exposure of the photoresist througha mask or reticle to actinic energy to modify the solubility of theexposed region relative to a suitable solvent. The imaging layer is thentypically solvent processed to remove one or the other of the processedor non-processed regions, thereby forming the photoresist layer to havemask openings extending entirely therethrough to the underlying layer tobe patterned. Typically, the substrate is then subjected to a suitableetching chemistry which is selected to etch the underlying layer orlayers and little if any of the photoresist, thereby transferring theimaging pattern to the underlying circuitry layer or layers.Alternately, other processing might be conducted through the patternedopenings (i.e., ion implantation) to otherwise form a suitable desiredpattern in the underlying layer or layers.

[0004] The photoresists utilized are typically entirely transmissive ofthe actinic energy utilized for their exposure. Unfortunately, someunderlying layers are highly reflective of the incident actinic energy,thereby reflecting a substantial quanta back into the photoresist. Thiscan adversely affect resolution and depth of focus, resulting in a lessthan desired transfer of the mask or reticle pattern into thephotoresist.

[0005] One known method of reducing such reflection is to provide anantireflective coating over the layer to be patterned prior to thedeposition of a photoresist layer thereover. The exposure to actinicenergy is thereby intended to be absorbed by the antireflective coatingas opposed to reflected back into the photoresist layer. After theexposing to actinic energy, the photoresist is then typically wetprocessed to form the openings therethrough to the antireflectivecoating. Thereafter, a different and dry chemistry processing istypically utilized to extend the openings from the photoresist throughthe antireflective coating to the ultimately desired layer therebeneathto be patterned.

[0006] One common antireflective coating material includes an inorganicsilicon oxynitride layer. Organic antireflective coatings are also knownin the art.

SUMMARY

[0007] The invention includes semiconductor processing methods which usephotoresist and antireflective coatings. In one implementation, asemiconductor processing method includes forming an antireflectivecoating comprising Ge and Se over a substrate to be patterned.Photoresist is formed over the antireflective coating. The photoresistis exposed to actinic radiation effective to pattern the photoresist.The antireflective coating reduces reflection of actinic radiationduring the exposing than would otherwise occur under identicalconditions in the absence of the antireflective coating. After theexposing, the substrate is patterned through openings in the photoresistand the antireflective coating using the photoresist and theantireflective coating as a mask. In one implementation, afterpatterning the substrate, the photoresist and the antireflective coatingare chemically etched substantially completely from the substrate usinga single etching chemistry.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

[0009]FIG. 1 is a diagrammatic perspective view of a semiconductor waferfragment/section in process in accordance with an aspect of theinvention.

[0010]FIG. 2 is a view of the FIG. 1 wafer fragment at a processing stepsubsequent to that shown by FIG. 1.

[0011]FIG. 3 is a view of the FIG. 2 wafer fragment at a processing stepsubsequent to that shown by FIG. 2.

[0012]FIG. 4 is a view of the FIG. 3 wafer fragment at a processing stepsubsequent to that shown by FIG. 3.

[0013]FIG. 5 is a view of the FIG. 4 wafer fragment at a processing stepsubsequent to that shown by FIG. 4.

[0014]FIG. 6 is a view of the FIG. 5 wafer fragment at a processing stepsubsequent to that shown by FIG. 5.

[0015]FIG. 7 is a view of the FIG. 6 wafer fragment at a processing stepsubsequent to that shown by FIG. 6.

[0016]FIG. 8 is a view of the FIG. 7 wafer fragment at a processing stepsubsequent to that shown by FIG. 7.

[0017]FIG. 9 is a view of the FIG. 8 wafer fragment at a processing stepsubsequent to that shown by FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] This disclosure of the invention is submitted in furtherance ofthe constitutional purposes of the U.S. Patent Laws “to promote theprogress of science and useful arts” (Article 1, Section 8).

[0019] A semiconductor wafer fragment in process, in accordance with thepreferred implementation of the invention, is depicted in FIG. 1 withthe numeral 10. Such comprises a bulk monocrystalline silicon substrate12 having a silicon nitride comprising layer 14 formed thereover. In thecontext of this document, the term “semiconductor substrate” or“semiconductive substrate” is defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove. Also in the context of this document, the term “layer”encompasses both the singular and the plural unless otherwise indicated.

[0020] Referring to FIG. 2, an antireflective coating 16 has been formedover the substrate 10 of FIG. 1. Antireflective coating 16 comprisesboth germanium and selenium. Preferably, the antireflective coatingcontains at least 30 atomic percent germanium and at least 50 atomicpercent selenium. More specifically, a more preferred concentrationrange for the germanium is from 30 atomic percent to 50 atomic percent,more preferably from about 38 atomic percent to about 42 atomic percent,with 40 atomic percent being a specific preferred example. A specificpreferred concentration for the selenium is 60 atomic percent. Mostpreferably, the antireflective coating consists essentially of germaniumand selenium. An example process for depositing the germanium andselenium comprising material includes physical vapor deposition, such asfor example sputtering using a target comprised of Ge_(x)S_(y), withexemplary ranges for “x” and “y” being from 0.38 to 0.42 and from 0.58to 0.62, respectively. An exemplary preferred thickness range for layer16 is from 100 Angstroms to 500 Angstroms. Further preferably,antireflective coating 16 is substantially amorphous. In the context ofthis document, “substantially amorphous” means being at least 90 percentby volume in the amorphous phase. Further preferably, antireflectivecoating 16 is also homogenous.

[0021] Referring to FIG. 3, a layer of photoresist 18 is formed overantireflective coating 16, and preferably on (in contact therewith)antireflective coating 16, as shown. Any suitable photoresist, whetherexisting or yet-to-be-developed, is contemplated and regardless ofwhether such comprises a positive or negative type photoresist. By wayof example only, exemplary photoresists include stepper operablephotoresists, such as MIO84 and SEPR 402.

[0022] Referring to FIG. 4, photoresist 18 has been exposed to actinicradiation (preferably, and by way of example only, using a mask orreticle) to pattern such photoresist. FIG. 4 depicts an exemplarypatterned and exposed portion 20 of layer 18, indicated by stippling ofsuch region entirely through layer 18. Antireflective coating 16 reducesreflection of the actinic radiation during the exposing than wouldotherwise occur under identical conditions in the absence of theantireflective coating, and thereby preferably enhances the patternedtransfer to layer 18.

[0023] Referring to FIG. 5, an opening 22 is formed in photoresist 18 bysuitable processing to remove the exemplary exposed portion depicted inFIG. 4. One preferred method is by conventional solvent processing, forexample which removes the processed portion relative to the unprocessedportion, effective to form the illustrated opening 22.

[0024] Referring to FIG. 6, subsequent etching is conducted ofantireflective coating 16 through photoresist openings 22. Such etchingis most preferably dry and anisotropic effective to substantiallytransfer the opening pattern 22 within photoresist layer 18 intoantireflective coating material 16. Less preferred would be wet etchingof layer 16 through opening 22. One exemplary dry method for removingmaterial 16 includes exposure to oxygen (i.e., O₂) at a temperature ofless than or equal to about 100° C. in a plasma environment. Anexemplary pressure includes at or below 1 Torr and an applied plasmapower of 1500 Watts. Such etching might also anisotropically etch someof the photoresist. Another exemplary process is dry etching in anammonia containing plasma atmosphere.

[0025] Exemplary preferred wet etchings include an ammonium hydroxidesolution. One exemplary such solution is tetramethyl ammonium hydroxide.Exemplary processing conditions preferably provide the solution at about25° C. and atmospheric pressure with the concentration of tetramethylammonium hydroxide, or other ammonium hydroxide, being from about 1percent to 50 percent by volume, with at about 2.5 percent being aspecific preferred example. Antireflective coating 16 might also beetched by these or another high pH solution, with a preferred pH beingfrom about 9 to about 13.

[0026] Referring to FIG. 7, silicon nitride comprising layer 14 isillustrated as having been subtractively etched through openings 22 inthe photoresist and the antireflective coating using the photoresist andthe antireflective coating as a mask. By way of example only, exemplaryprocessing conditions for conducting the above-illustrated etch includea pressure of 20 mTorr, power at 800 W, temperature from 200° C. to 600°C., CHF₃ flow at 22 sccm, and CH₂F₂ flow at 18 sccm for from 10 secondsto 100 seconds.

[0027] Such provides but one example of patterning the substrate throughopenings in the photoresist and the antireflective coating, using thephotoresist and the antireflective coating as a mask. Any other possiblealternate patterning through the openings, whether existing oryet-to-be-developed, is also of course contemplated. By way of exampleonly, one such alternate exemplary processing would be ion implantationinto the layer or layers beneath antireflective coating material 16 asopposed to, or in addition to, subtractive etching thereof.

[0028] Referring to FIG. 8, photoresist layer 18 has been substantiallycompletely removed from the substrate. Exemplary processing forconducting the same includes exposure to an oxygen containing plasma,for example as referred to above. Wet processing to produce theillustrated FIG. 8 construction might also be conducted, for example, byremoving the photoresist in a sulfuric acid and hydrogen peroxidesolution.

[0029]FIG. 9 illustrates subsequent removal of antireflective coating16. Exemplary processes for doing so include any of those describedabove for removing material 16 to extend contact openings 22 to theunderlying substrate layers.

[0030] The invention also contemplates chemically etching thephotoresist and the antireflective coating substantially completely fromthe substrate using a single etching chemistry, for example going in asubstantial single etching chemistry step from the FIG. 7 to the FIG. 9construction. For example, such might be conducted utilizing a dryetching chemistry by exposure to an oxygen plasma containing atmosphere,preferably at a temperature above 100° C., effective to completely etchboth photoresist 18 and antireflective coating 16 from the substrate,for example preferably in a single/common processing step. Such removalof a germanium and selenium containing antireflective coating might befacilitated by exposing the antireflective coating through thephotoresist to radiation having a wavelength from about 190 nanometersto about 450 nanometers, and thereafter dry etching the antireflectivecoating in an oxygen comprising ambient. Such might be conducted as perthe above for extending the photoresist openings through theantireflective coating material 16 to the underlying substrate, or inconjunction with a preferred implementation of completely removingphotoresist and the antireflective coating material from the substrateusing a single etching chemistry, and preferably in a single/commonetching step. Further, the exposing of the antireflective coatingthrough the photoresist to radiation having a wavelength from about 190nanometers to about 450 nanometers could, of course, be conducted eitherprior to or after solvent processing of the photoresist to form theinitial opening 22 therethrough.

[0031] In compliance with the statute, the invention has been describedin language more or less specific as to structural and methodicalfeatures. It is to be understood, however, that the invention is notlimited to the specific features shown and described, since the meansherein disclosed comprise preferred forms of putting the invention intoeffect. The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A semiconductor processing method, comprising: forming anantireflective coating comprising Ge and Se over a substrate to bepatterned; forming photoresist over the antireflective coating; exposingthe photoresist to actinic radiation effective to pattern thephotoresist, the antireflective coating reducing reflection of actinicradiation during the exposing than would otherwise occur under identicalconditions in the absence of the antireflective coating; and after theexposing, patterning the substrate through openings in the photoresistand the antireflective coating using the photoresist and theantireflective coating as a mask.
 2. The method of claim 1 wherein theantireflective coating consists essentially of Ge and Se.
 3. The methodof claim 1 wherein the antireflective coating consists essentially ofabout 40 atomic per cent Ge and about 60 atomic percent Se.
 4. Themethod of claim 1 wherein the antireflective coating is substantiallyamorphous.
 5. The method of claim 1 wherein the antireflective coatingcomprises at least 30 atomic percent Ge.
 6. The method of claim 1wherein the antireflective coating comprises from 30 atomic percent to50 atomic percent Ge.
 7. The method of claim 1 wherein theantireflective coating comprises from 38 atomic percent to 42 atomicpercent Ge.
 8. The method of claim 1 wherein the photoresist contactsthe antireflective coating.
 9. The method of claim 1 wherein patterningthe substrate comprises subtractive etching.
 10. The method of claim 1comprising after the patterning, removing substantially all thephotoresist and antireflective coating layer from the substrate.
 11. Themethod of claim 1 wherein the openings in the photoresist and theantireflective coating are formed by solvent processing of thephotoresist after the exposing to form the photoresist openings,followed by dry etching of the antireflective coating through thephotoresist openings.
 12. The method of claim 11 wherein forming theopenings in the antireflective coating comprises after said exposing,exposing the antireflective coating through the photoresist to radiationhaving a wavelength from about 190 nanometers to about 450 nanometers,and thereafter dry etching the antireflective coating in an oxygencomprising ambient.
 13. A semiconductor processing method, comprising:forming an antireflective coating comprising at least 30 atomic percentGe and at least 50 atomic percent Se over a substrate to be patterned;forming photoresist over the antireflective coating; exposing thephotoresist to actinic radiation effective to pattern the photoresist,the antireflective coating reducing reflection of actinic radiationduring the exposing than would otherwise occur under identicalconditions in the absence of the antireflective coating; and after theexposing, patterning the substrate through openings in the photoresistand the antireflective coating using the photoresist and theantireflective coating as a mask.
 14. The method of claim 13 wherein theopenings in the photoresist and the antireflective coating are formed bysolvent processing of the photoresist after the exposing to form thephotoresist openings, followed by dry etching of the antireflectivecoating through the photoresist openings.
 15. The method of claim 14wherein the dry etching comprises exposure to oxygen at a temperature ofat least 100° C.
 16. The method of claim 14 wherein forming the openingsin the antireflective coating comprises after said exposing, exposingthe antireflective coating through the photoresist to radiation having awavelength from about 190 nanometers to about 450 nanometers, andthereafter dry etching the antireflective coating in an oxygencomprising ambient.
 17. The method of claim 16 wherein said exposing ofthe antireflective coating through the photoresist to radiation having awavelength from about 190 nanometers to about 450 nanometers occursprior to said solvent processing of the photoresist.
 18. The method ofclaim 16 wherein said exposing of the antireflective coating through thephotoresist to radiation having a wavelength from about 190 nanometersto about 450 nanometers occurs after said solvent processing of thephotoresist.
 19. The method of claim 14 wherein the dry etchingcomprises exposure to an NH₃ comprising plasma.
 20. The method of claim13 wherein the openings in the photoresist and the antireflectivecoating are formed by solvent processing of the photoresist after theexposing to form photoresist openings, followed by wet etching of theantireflective coating through the photoresist openings.
 21. The methodof claim 20 wherein the wet etching comprises exposure to an ammoniumhydroxide comprising solution.
 22. The method of claim 20 wherein thewet etching comprises exposure to a tetramethyl ammonium hydroxidecomprising solution.
 23. The method of claim 20 wherein the wet etchingcomprises exposure to a solution having a pH of at least
 9. 24. Themethod of claim 13 wherein the antireflective coating consistsessentially of Ge and Se.
 25. The method of claim 13 wherein theantireflective coating is substantially amorphous.
 26. The method ofclaim 13 wherein patterning the substrate comprises subtractive etching.27. The method of claim 13 comprising after the patterning, removingsubstantially all the photoresist and antireflective coating layer fromthe substrate.
 28. A semiconductor processing method, comprising:forming a silicon nitride comprising layer over a substrate; forming anantireflective coating comprising Ge and Se over the silicon nitridecomprising layer; forming photoresist over the antireflective coating;exposing the photoresist to actinic radiation effective to pattern thephotoresist, the antireflective coating reducing reflection of actinicradiation during the exposing than would otherwise occur under identicalconditions in the absence of the antireflective coating; and after theexposing, subtractively etching the silicon nitride comprising layerthrough openings in the photoresist and the antireflective coating usingthe photoresist and the antireflective coating as a mask.
 29. The methodof claim 28 comprising after the patterning, removing substantially allthe photoresist and antireflective coating layer from the substrate. 30.The method of claim 28 wherein the antireflective coating consistsessentially of Ge and Se.
 31. The method of claim 28 wherein theantireflective coating comprises at least 30 atomic percent Ge.
 32. Themethod of claim 28 wherein the antireflective coating comprises from 30atomic percent to 50 atomic percent Ge.
 33. The method of claim 28wherein the antireflective coating comprises from 38 atomic percent to42 atomic percent Ge.
 34. The method of claim 28 wherein the openings inthe photoresist and the antireflective coating are formed by solventprocessing of the photoresist after the exposing to form the photoresistopenings, followed by dry etching of the antireflective coating throughthe photoresist openings.
 35. The method of claim 34 wherein forming theopenings in the antireflective coating comprises after said exposing,exposing the antireflective coating through the photoresist to radiationhaving a wavelength from about 190 nanometers to about 450 nanometers,and thereafter dry etching the antireflective coating in an oxygencomprising ambient.
 36. A semiconductor processing method, comprising:forming an antireflective coating comprising Ge and Se over a substrateto be patterned; forming photoresist over the antireflective coating;exposing the photoresist to actinic radiation effective to pattern thephotoresist, the antireflective coating reducing reflection of actinicradiation during the exposing than would otherwise occur under identicalconditions in the absence of the antireflective coating; after theexposing, patterning the substrate through openings in the photoresistand the antireflective coating using the photoresist and theantireflective coating as a mask; and after patterning the substrate,chemically etching the photoresist and the antireflective coatingsubstantially completely from the substrate using a single etchingchemistry.
 37. The method of claim 36 wherein the single etchingchemistry is wet.
 38. The method of claim 36 wherein the single etchingchemistry is dry.
 39. The method of claim 36 wherein the single etchingchemistry is dry and comprises exposure to an oxygen plasma containingatmosphere.
 40. The method of claim 36 wherein the single etchingchemistry is dry and comprises exposure to an oxygen plasma containingatmosphere.
 41. The method of claim 36 wherein the antireflectivecoating consists essentially of Ge and Se.
 42. The method of claim 36wherein the antireflective coating consists essentially of about 40atomic per cent Ge and about 60 atomic percent Se.
 43. The method ofclaim 36 wherein the antireflective coating is substantially amorphous.44. The method of claim 36 wherein the antireflective coating comprisesat least 30 atomic percent Ge.
 45. The method of claim 36 wherein theantireflective coating comprises from 30 atomic percent to 50 atomicpercent Ge.
 46. The method of claim 36 wherein the antireflectivecoating comprises from 38 atomic percent to 42 atomic percent Ge. 47.The method of claim 36 wherein the openings in the photoresist and theantireflective coating are formed by solvent processing of thephotoresist after the exposing to form the photoresist openings,followed by dry etching of the antireflective coating through thephotoresist openings.
 48. The method of claim 47 wherein forming theopenings in the antireflective coating comprises after said exposing,exposing the antireflective coating through the photoresist to radiationhaving a wavelength from about 190 nanometers to about 450 nanometers,and thereafter dry etching the antireflective coating in an oxygencomprising ambient.